This invention relates in general to bearings which take axial as well as radial loads and, more particularly, to a process and tool for adjusting such bearings.
Some bearings have the capacity to transfer axial or thrust loads as well as radial loads, and when single row bearings of this character are organized in pairs, one opposing the other, they are well suited for a wide variety of machine applications, none the least of which is in mountings for the road wheels of automotive vehicles. But the bearings, when so organized, require adjustment during installation to achieve the proper setting for operation. If they are set with too much end play, a limited amount of free radial and axial motion exists in the mounting which may manifest itself in wheel wobble. In short, the mounting is not as stable as it should be. Furthermore, excessive end play causes the load zone to concentrate at a few rollers, and this may diminish the life of the bearing. Preload, on the other hand, produces a very rigid mounting, but also imparts more friction to the bearings and may cause the bearings to fail early. In most mountings it is desirable to have the bearings set near a condition often referred to as "zero end play", that is to say with a very slight amount of end play or a very slight amount of preload.
Automotive wheel bearings present a problem because they are often disassembled for inspection and lubrication, or for work on related components, such as brakes, at shops which do not have tools for accurately adjusting the bearings on reassembly. To be sure, many garages adjust the bearings for the nondriven wheels of automobiles simply by turning the spindle nuts which hold the bearings on their respective spindles, indeed turning those nuts until they feel reasonably tight. This provides a reasonably accurate setting, because the wheels are small and light in weight, making it easy to detect simply by feel the appropriate point at which all end play is eliminated. But some automotive wheels, such as those found on trucks, are much larger and heavier, and as a consequence it is difficult if not impossible to detect by feel the point at which end play is removed from the bearings.
One can adjust the bearings for a truck wheel by making incremental advances of the nut that holds the bearings on their spindle and between such advances making measurements of end play with a dial indicator. In a conventional adjusting procedure, the spindle nut is turned to a specific torque, while the wheel is oscillated to seat the rollers along the races. Next the nut is backed off one turn, retightened, again while the wheel is oscillated, until a lesser nut torgue is achieved, and then backed off again a specified amount, which to a measure depends on the pitch of the spindle thread. With a jam nut turned down against the spindle nut, the end play is measured using a dial indicator. To this end, the mechanic installs the indicator on the wheel with its stylus against the spindle end and moves the wheel axially back and forth while oscillating it, observing the reading on the indicator as he does. If excessive end play appears, the mechanic backs the jam nut off, advances the spindle nut slightly, with the magnitude of the amount being largely based on experience, tightens the jam nut, and makes another measurement. If insufficient end play exists, the mechanic follows essentially the same procedure, but backs the spindle nut off instead of turning it down. This trial and error procedure is repeated until the measured end play falls within an acceptable range.
In any event, the adjustment is made with the wheel mounted on the spindle yet elevated above the ground. Owing to the weight of the wheel, the mechanic has difficulty moving it inwardly and outwardly along the spindle axis to ascertain the extent of the end play. Furthermore, many service facilities do not have for their immediate use dial indicators required for implementing the procedure. Apart from that, dial indicators are delicate instruments which are easily damaged in a garage.
The present invention resides in a process for adjusting bearings while they are off their normal mounting, which may be a spindle, yet within a hub or other component that fits over the normal mounting. The invention also resides in a tool for making the adjustment.